Biomedical Engineering Reference
In-Depth Information
For high luster, it is important that the flakes
are properly dispersed in the cosmetic product
to prevent agglomeration, but all have the same
orientation
[130]
. Pearlescents reflect better when
they have what is known as a
background color
.
A red pigment on a red background looks
even more intense than on its own. Even though
pearlescents are widely used in retail eye make-
up, most eye shadows contain less than 10%
pearlescent pigments; the rest is filler material.
Although a wide variety of vivid interference
colors and a pearly luster are produced, the
addition of colored compounds to cosmetic
products comprising nacreous pigments reduces
the shelf life and may cause safety concerns.
FIGURE 11.28
Schematic of a mica flake used by
Shiseido in its
Infinite Color
TM
line of cosmetic products,
after Ref.
131
.
11.6.4.3 The Infinite Color
TM
of Shiseido
Infinite Color
TM
, the first purely physical color for
cosmetic applications, was developed by the Jap-
anese cosmetics company Shiseido after compre-
hensive research on nacreous paints for cosmetics
[134]
. Established in 1872 as the first Western-style
pharmacy in Japan, Shiseido now is the leading
cosmetics company in that country.
Infinite Color
TM
is a photochromic formulation of titanium dioxide
whose color changes with the viewing angle. The
pigment consists of fine mica flakes coated with
titanium dioxide and its lower oxides Ti
n
O
2
n
−
1
(
n
=
1, 2, 3,
...
)
[131]
. The mica flake is coated
first with a black lower titanium oxide, shown in
the example sketch of an
Infinite Color
TM
flake in
Figure 11.28
as Ti
4
O
7
, and then coated with tita-
nium dioxide. As shown in
Table 11.3
, the lower
oxides of titanium are bluish or purplish black
in color and their role is to provide a black back-
ground. This black layer is very stable; it absorbs
the transmitted light and causes the interference
phenomenon to be greatly enhanced.
Table 11.4
provides some examples of colors by
Infinite
Color
TM
and the corresponding optical thickness
of the coated mica flakes.
In comparing the
Infinite Color
TM
with the pear-
lescent pigments used in cosmetics, it is worth
stressing that the
Infinite Color
TM
is produced only
by interference of light, without the addition of
TABLE 11.3
Color of black lower oxide of titanium in
Infinite Color
TM
[131]
.
Composition
Color
TiO
Bronze
Ti
2
O
3
Purplish black
Ti
3
O
5
Bluish black
Ti
4
O
7
Bluish black
TABLE 11.4
Colors of
Infinite Color
TM
[131]
.
Interference
Colors as They
Appear
Base Color
Optical
Thickness (nm)
Gold
210
Red
Blue purple
250
Blue
310
Green
360
coloring materials, whereas the pearlescent cos-
metics also use dyes and other pigments. The
Infi-
nite Color
TM
has excellent hiding power and high
flip-flop effect, i.e., change of color with the view-
ing angle. Similarly to pearlescent pigments, when
the
Infinite Color
TM
is applied on black background,
both the pearly luster and the interference color
show. The difference is that when pearlescent pig-
ments are applied on a white background, the
